If your sunscreen smells weird or looks separated, toss it.

The answer is: trust your nose and eyes, and keep a mental three-year timer.

Sunscreen without a date is annoyingly common. The rule of thumb is that most sunscreens last about three years from the date of manufacture. If you don’t know when you bought it and it’s been sitting in your bathroom cabinet for a while, get suspicious.

Look for separation – if the lotion is watery, curdled, or there’s oil floating on top, it’s done. Smell it – a rancid, chemically, or just “off” odor means the preservatives have failed. Also, if the texture turns gritty or chunky, toss it. Sunscreen that’s expired will not protect you, and a sunburn is way worse than buying a new bottle.

When in doubt, throw it out. Sunscreen is cheap. Skin cancer is not.